JPS6228084B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved method for producing hydrated silicic acid. Hydrated silicic acid is generally agglomerated single particles of hydrated silicic acid with a particle size of 10 to 50 mμ, and is widely used as agricultural chemical carriers, rubber fillers, and various other uses. Conventionally, the properties of hydrated silicic acid used in the above-mentioned applications have been improved by increasing its oil absorption. Various conditions for producing hydrated silicic acid with high oil absorption have been studied and proposed. However, hydrated silicic acid whose oil absorption is merely increased does not necessarily satisfy the properties required for the above-mentioned uses. That is, hydrated silicic acid produced by conventional methods generally has a drawback of slow oil absorption rate. Therefore, for example, when producing agricultural chemicals using hydrated silicic acid as a carrier,
It takes a lot of time to adsorb agricultural chemical components to the hydrated silicic acid, resulting in a decrease in workability. In addition, when the hydrated silicic acid carrier that has adsorbed agricultural chemical components is crushed or mixed with other additives, the adsorbed agricultural chemical components are leached out and are transferred to the crusher or mixer into the carrier, other additives, etc. may adhere and cause trouble with the above equipment. The present inventors have discovered that the oil absorption rate of hydrated silicic acid is almost unrelated to the oil absorption amount of hydrated silicic acid, and that the volume occupied by pores with a pore radius of 150 Å or less in the pore size distribution of hydrated silicic acid (hereinafter simply referred to as We have found that this can be improved by increasing the pore volume (also called pore volume). As a result of intensive research based on the above knowledge, we found that hydrated silicic acid can be obtained by carrying out the reaction under specific conditions in a method for producing hydrated silicic acid by adding acid to an aqueous alkali silicate solution in multiple stages. It has been discovered that hydrated silicic acid can be obtained in which the pore volume of the acid is significantly increased and the oil absorption rate among the properties of hydrated silicic acid is improved, and the present invention has been completed. That is,
In the present invention, when producing hydrated silicic acid by adding mineral acids to an aqueous alkali silicate solution in multiple stages, the acid addition ratio (A) in the first stage is 20 to 50% and the second
The silica concentration (C) in the solution when adding step acid is 2
~6g/100c.c. and reaction temperature (T) of 70~100℃
and the formula X={1/T-65+(A/10)
〓}/C 〓〓 The volume occupied by pores with a pore radius of 150 Å or less in the pore size distribution is 0.5, which is characterized by performing the reaction under conditions where the value of X is 1.280 to 1.550.
This is a method for producing ~2.0cc/g hydrated silicic acid. As mentioned above, the oil absorption rate of hydrated silicic acid is significantly influenced by the pore volume of the hydrated silicic acid, and the larger the pore volume, the better the oil absorption rate of hydrated silicic acid. The hydrated silicic acid obtained by the method of the present invention has a pore volume of
It has a high oil absorption rate of 0.5 to 2.0 cc/g, especially 0.7 to 2.0 cc/g, and exhibits an excellent oil absorption rate. Incidentally, the pore volume of currently commercially available hydrated silicic acid is 0.11 to 0.45.
Most of them are cc/g. Note that the pore volume in the present invention is measured by a mercury porosimeter method unless otherwise specified, and is expressed by the formula r (Å) = 7.5 x 10 ⁴ /P.
(Kg/cm ² ) (edited by Powder Engineering Research Group and Japan Powder Industry Association, published by Industrial Technology Center Co., Ltd. (published on May 1, 1975)
This is the value calculated from "Illustrated Guide to Powder Physical Properties," pages 116 to 117). In the present invention, sodium silicate, potassium silicate, ammonium silicate, etc. are generally used as the alkali silicate. The alkali silicate has a molar ratio (M ₂ O/SiO ₂ ; M represents Na, K, NH ₄ , etc.)
2.0 to 4.0 is preferably used. As acids, mineral acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, and acid gases such as carbon dioxide gas and sulfur dioxide gas are generally used. In order to obtain hydrated silicic acid with a high oil absorption rate, which is the object of the present invention, it is necessary to carry out the reaction between the alkali silicate aqueous solution and the acid by adding the acid to the alkali silicate aqueous solution in multiple stages. do. That is,
A first stage of acid addition is performed to the aqueous alkali silicate solution. In the present invention, it is important that the ratio (A) of acid addition in the first stage is 20 to 50% of the acid required to neutralize all the alkali silicate. When the acid addition ratio in the first stage is lower than the above range, the single particles of the hydrated silicic acid produced become large, and the pore diameter of the hydrated silicic acid obtained by agglomeration of the single particles becomes large. Therefore, the pore volume of the obtained hydrated silicic acid cannot be increased even if the oil absorption is increased.
Furthermore, if the acid addition ratio in the first stage is higher than the above range, gelation is likely to occur and the pore volume of the resulting hydrated silicic acid is significantly reduced, making it difficult to obtain hydrated silicic acid with a high oil absorption rate. Can not. Although the temperature in the first stage of acid addition is not particularly limited, it is generally preferred to carry out the acid addition at a low temperature of 10 to 65°C in order to increase the pore volume of the resulting hydrated silicic acid. Furthermore, when adding the acid in the first stage, appropriate stirring is generally desirable in order to prevent local reactions and prevent gelation. After the first stage of acid addition is completed, the reaction temperature is maintained with continued stirring to precipitate hydrated silicic acid seeds. In the present invention, the reaction temperature (T) is set at 70 to 100.
It is also very important to choose from the range of °C. When the reaction temperature is lower than the above range, gelation tends to occur;
Since the pore volume of the resulting hydrated silicic acid is significantly reduced, hydrated silicic acid with a high oil absorption rate cannot be obtained. Furthermore, if the reaction temperature is higher than the above range, the amount of water evaporated during the reaction will increase, and the silica concentration in the reaction system will fluctuate, making it impossible to carry out a stable reaction. In particular, in the present invention, the first stage of acid addition is performed at a temperature lower than the reaction temperature, for example, 10 to 65°C, and then the temperature is raised and maintained at the reaction temperature to precipitate hydrated silicic acid. This is preferred in terms of obtaining hydrated silicic acid with a large pore volume. Next, after the first stage acid addition is completed, when adding the second stage acid, the silica concentration (C) in the solution is 2 to 6 g/
It is important that it is adjusted to 100c.c. The silica concentration (C) can be determined by dividing the weight of silica in the starting alkali silicate aqueous solution by the volume of the total solution. The silica concentration (C) is determined by the concentration and molar ratio of the raw material alkali silicate aqueous solution, the amount of water added,
It can be adjusted by adjusting the amount and concentration of the acid added in the first stage, or the amount of condensed water when steam is blown into the solution to maintain the above-mentioned reaction temperature. Note that when adding the second stage acid, if the silica concentration (C) in the solution is lower than the above range, the pore volume of the hydrated silicic acid obtained will increase somewhat, but the amount of water in the reaction system will increase. Not only does this increase the size of the equipment, but it also requires a large amount of energy for heating, filtration, etc., which is economically disadvantageous. Furthermore, if the silica concentration (C) is higher than the above range, gelation is likely to occur and the pore volume of the resulting hydrated silicic acid is significantly reduced, making it impossible to obtain hydrated silicic acid with a high oil absorption rate. In the present invention, the second stage of acid addition is preferably started after the first stage of acid addition is completed, at a time when the viscosity of the solution reaches its maximum due to precipitation of hydrated silicic acid seeds. The start time of the above acid addition varies depending on conditions such as the first stage acid addition temperature, the first stage acid addition ratio, and the reaction temperature, but generally 25 to 40 minutes after the first stage acid addition is completed. It's a minute later. Further, in the present invention, after the first stage of acid addition is completed, the remaining acid can be added continuously or in multiple stages while maintaining the above reaction temperature. In the present invention, the silica concentration in the solution (C) when adding the above-mentioned second-stage acid, the ratio of first-stage acid addition to the total amount of acid added (A), and reaction temperature (T) As a result of various statistical experiments using the function as a function, the formula X={1/T-65+(A/10)}/C
It has been found that it is extremely important to carry out the reaction so that the value of X, represented by . In other words, if the value of Hydrated silicic acid cannot be obtained. Furthermore, if the value of X is higher than the above range, gelation is likely to occur and the pore volume is significantly reduced, making it impossible to obtain hydrated silicic acid with a high oil absorption rate. In the present invention, other conditions such as adding an electrolyte such as an alkali metal salt or an alkaline earth metal salt during the reaction, and performing post-treatment such as hydrothermal treatment on the hydrated silicic acid slurry obtained after the reaction is completed. This can be carried out as necessary. Further, the obtained hydrated silicic acid slurry is filtered and dried by a known method. For example, as a filter, a filter press type, a rotary type, etc. are generally used, and as a dryer, a rotary type, a band type, a turbo type, an airflow type, a spray type, etc. are generally used. The hydrated silicic acid obtained by the method of the invention has an especially improved oil absorption rate. Therefore, when the hydrated silicic acid obtained by the method of the present invention is used, for example, as a carrier for agricultural chemicals, the rate of adsorption of agricultural chemical components is fast, and furthermore, even when the agricultural chemical components are mixed or crushed after adsorption, the leaching of the agricultural chemical components is prevented. It fully satisfies the properties required for agricultural chemical carriers, such as no oxidation and excellent workability. Further, the hydrated silicic acid obtained by the method of the present invention is suitably used not only as a carrier for agricultural chemicals but also as a rubber filler and other uses. EXAMPLES In order to explain the present invention in more detail, Examples and Comparative Examples will be given below, but the present invention is not limited to these Examples. The pore volume, crushing test, dispersibility test, oil absorption rate, apparent specific gravity, and oil absorption of hydrated silicic acid in Examples and Comparative Examples were measured by the following methods. (1) Pore volume: The pore volume is 1520 type mercury porosiometer (Dilatometer type SM3, manufactured by CARLOERBA), Capillary: 3 mmφ
0.07065cm ² ). Note that the pore volume was expressed as a volume of 50 to 150 Å. (2) Grinding test: Take 5 g of hydrated silicic acid sample in an evaporating dish. Add 10 ml of boiled oil to the sample and let it adsorb onto the sample. The above sample was ground using a Philips coffee mill (for home use), and the time required for the boiling oil adsorbed to the sample to leach out during the grinding and for the sample to form a lump was measured. (3) Dispersibility test: Take 5 g of hydrated silicic acid sample in an evaporation dish. Add 10 ml of boiled oil to the sample and let it adsorb onto the sample. The above sample was sieved through a 20-mesh sieve, and the weight on the sieve was measured. (4) Oil absorption rate: Figures 1 to 3 are schematic diagrams showing a method for measuring oil absorption rate. The hydrated silicic acid sample 2 under the sieve, which has been separated using a 32-mesh sieve, is placed in a container 1 with an open top, 70 mm in diameter and 16 mm in height, up to the angle of repose of the sample, as shown in FIG. Next, as shown in FIG. 2, a weight 3 is placed on a watch glass 4 having a diameter of 110 mm to give a total weight of 100 g, and a weight is placed on the sample, compressed, and lifted after 15 seconds. Then, as shown in Figure 3, 2 ml of boiled oil 5 was dropped onto the surface of the compressed sample, and the time required from the time the boiled oil and the sample came into contact until all the boiled oil was absorbed into the sample was measured. . The measurements were conducted indoors at a temperature of 20°C. (5) Apparent specific gravity: Performed according to JISK6220. (6) Oil absorption: Conformed to JISK6220. Example 1 A commercially available sodium silicate aqueous solution (molar ratio 3.03, silica concentration 26.4%) 7.6, Boron's salt aqueous solution (Na ₂ O concentration)
1.48%) 33.8% and water 3.64% were fed into an internally heated reactor with an internal volume of 60 and a stirrer. Next, sulfuric acid (22 g/100
cc) 1.99 was added in approximately 10 minutes. Table 1 shows the ratio (A) of the sulfuric acid added to the total amount of acid added. After the acid addition in the first stage was completed, water vapor was blown into the reactor while stirring was continued, and the temperature was raised to the predetermined reaction temperature (T) shown in Table 1 in 20 minutes. The silica concentration (C) at this time is shown in Table 1. After keeping the solution at reaction temperature for another 10 minutes, add the remaining 2.9 sulfuric acid while continuing to stir.
The reaction was terminated by continuous addition over 90 minutes. the above
Table 1 shows the (X) values determined from (C), (A), and (T). The reaction solution has a pH of hydrated silicic acid after drying.
After adjusting the pH to 5.5 to 7.0, filtering and washing with water, it was dried in a stationary dryer and ground in a ball mill to obtain hydrated silicic acid. Table 1 shows the results of measurements of pore volume, crushing test, dispersibility test, oil absorption rate, apparent specific gravity, and oil absorption of the obtained hydrated silicic acid. Example 2 In Example 1, the amount of sulfuric acid added in the first stage was
Hydrated silicic acid was obtained in the same manner except that the amount of added sulfuric acid was changed to 1.74, the remaining amount of sulfuric acid was changed to 3.08, and the reaction temperature was changed. Table 1 shows silica concentration (C), acid addition ratio (A),
Reaction temperature (T) and (X) values are shown. In addition, the results of the same measurements and tests as in Example 1 are shown in the first
Shown in the table. Example 3 The same sodium silicate aqueous solution and Boron's nitrate aqueous solution as in Example 1 were supplied at 2.27 and 13.5, respectively, and water at 2.02 to an internally heated reaction tank having an internal volume of 25 and equipped with a stirrer. Then, 0.44 ml of sulfuric acid (22 g/100 c.c.) was added over about 10 minutes at a temperature in the range of 40 to 45° C. while stirring. The addition ratio (A) of the above sulfuric acid is shown in Table 1. After the first stage of acid addition was completed, water vapor was blown into the reaction mixture while stirring was continued, and the temperature was raised to the reaction temperature (T) shown in Table 1 in 20 minutes. The silica concentration (C) at this time is shown in Table 1. The solution was then kept at the above reaction temperature for 10 minutes, and then the remaining 1.03% of sulfuric acid was added with continued stirring.
was added continuously over 100 minutes to terminate the reaction. the above
Table 1 shows the (X) values determined from (C), (A), and (T). Thereafter, hydrated silicic acid was obtained in the same manner as in Example 1. The obtained hydrated silicic acid was subjected to the same measurements and tests as in Example 1, and the results are shown in Table 1. Example 4 The same sodium silicate aqueous solution and Boron's nitrate aqueous solution as in Example 1 were supplied at 6.1 and 27.0, respectively, and water at 6.9 to an externally heated reaction tank having an internal volume of 50 and equipped with a stirrer. Then, 1.58 g of sulfuric acid (22 g/100 c.c.) was added over about 10 minutes at a temperature of 40 to 45° C. while stirring. The addition ratio (A) of the above sulfuric acid is shown in Table 1. The silica concentration (C) at this time is shown in Table 1. After completing the first stage of acid addition, the first stage was added for 20 minutes while continuing to stir.
The temperature was raised to a predetermined reaction temperature (T) shown in the table. After the solution was kept at the above reaction temperature for 10 minutes, the remaining 2.29 g of sulfuric acid was continuously added over 100 minutes while stirring to complete the reaction. Table 1 shows the (X) values determined from (C), (A), and (T) above. Thereafter, hydrated silicic acid was obtained in the same manner as in Example 1. The obtained hydrated silicic acid was subjected to the same measurements and tests as in Example 1, and the results are shown in Table 1. Example 5 Using a sodium silicate aqueous solution, a saltwater solution, and a reaction tank similar to those in Example 4, a sodium silicate aqueous solution was prepared.
8.79, 27.0% of Bow's salt aqueous solution, and 4.2% of water were supplied to the reaction tank. Below, the amount of sulfuric acid added in the first stage is 2.56
, the remaining amount of sulfuric acid added to 3.03, and
Hydrated silicic acid was obtained in the same manner as in Example 1 except that the reaction temperature was changed. Table 1 shows the silica concentration (C), acid addition ratio (A), reaction temperature (T), and (X) values.
Table 1 shows the results of the same measurements and tests as in Example 1. Comparative Example 1 In Example 1, the amount of sulfuric acid added in the first stage was
Hydrated silicic acid was obtained in the same manner except that the amount of added acid was changed to 1.47 and the remaining amount of acid added was changed to 3.35. Table 1 shows silica concentration (C), acid addition ratio (A), and reaction temperature (T).
and (X) value. Further, the results of measurements and tests similar to those in Example 1 are shown in Table 1. Comparative Example 2 4 of the same sodium silicate aqueous solution as in Example 1, 13.3 of a sulfate aqueous solution (Na ₂ O concentration 1.35%), and 0.9 of water were supplied to a reaction tank similar to that of Example 3. Next, sulfuric acid (22 g/
100 c.c.) 0.9 was added in 22 minutes. The addition ratio (A) of the above sulfuric acid is shown in Table 1. After the first stage of acid addition was completed, steam was blown into the reactor while stirring was continued, and the temperature was raised to the reaction temperature (T) shown in Table 1 over 30 minutes.
The silica concentration (C) at this time is shown in Table 1. After the solution was kept at the reaction temperature for further 10 minutes, the remaining 1.95 ml of sulfuric acid was continuously added over 50 minutes while stirring was continued to terminate the reaction. Table 1 shows the (X) values determined from (C), (T), and (A) above. Thereafter, hydrated silicic acid was obtained in the same manner as in Example 1. The obtained hydrated silicic acid was subjected to the same measurements and tests as in Example 1, and the results are shown in Table 1. Comparative Example 3 The same reaction tank as in Example 3 was used, and in the same manner as in Example 3, a sodium silicate aqueous solution, a sulfur salt aqueous solution, and water were supplied to the reaction tank. Next, 0.73 g of sulfuric acid (22 g/100 c.c.) was added at a temperature of 40 to 45°C while stirring.
was added over about 10 minutes. The addition ratio (A) of the above sulfuric acid is shown in Table 1. After the first stage of acid addition was completed, water vapor was blown into the mixture while stirring was continued, and the temperature was raised to the reaction temperature (T) shown in Table 1 over 20 minutes. The silica concentration (C) at this time is shown in Table 1. After the solution was further maintained at the above reaction temperature for 10 minutes, the remaining 0.71 ml of sulfuric acid was continuously added over 90 minutes while stirring was continued to complete the reaction. Table 1 shows the (X) values determined from (C), (A), and (T) above. Thereafter, hydrated silicic acid was obtained in the same manner as in Example 1. The obtained hydrated silicic acid was subjected to the same measurements and tests as in Example 1, and the results are shown in Table 1. Comparative Example 4 Using the same reaction tank as in Example 4, the same sodium silicate aqueous solution and Boron's nitrate aqueous solution as in Example 1 were respectively added.
10.6, 27.0 and water 2.4 were supplied to the reaction tank. Then, 2.06 ml of sulfuric acid (22 g/100 c.c.) was added over about 10 minutes at a temperature of 40 to 45° C. while stirring. The addition ratio (A) of the above sulfuric acid is shown in Table 1. After the first stage of acid addition was completed, steam was blown into the reactor while stirring was continued, and the temperature was raised to the reaction temperature shown in Table 1 in 20 minutes. The silica concentration (C) at this time is shown in Table 1. After keeping the solution at the above reaction temperature for further 10 minutes, the remaining 4.65 ml of sulfuric acid was continuously added over 100 minutes while stirring was continued to complete the reaction. (C), (A), (T) above
The (X) values obtained are shown in Table 1. below,
Hydrated silicic acid was obtained in the same manner as in Example 1. The obtained hydrated silicic acid was subjected to the same measurements and tests as in Example 1, and the results are shown in Table 1. Comparative Example 5 In Example 4, the amount of sulfuric acid added in the first stage was changed to 0.59.
Next, hydrated silicic acid was obtained in the same manner except that the remaining amount of sulfuric acid added was changed to 3.25 and the reaction temperature was changed. Table 1 shows the silica concentration (C), acid addition ratio (A), reaction temperature (T) and (X) values. In addition, Example 1
Table 1 shows the results of measurements and tests similar to those described above. Comparative Example 6 Using the same reaction tank as in Example 4, the same sodium silicate aqueous solution and Boron's nitric acid aqueous solution as in Example 1 were respectively applied.
4.5, served 27 and water 8.5. Hereinafter, in Example 4, the amount of sulfuric acid added in the first stage was set to 1.60,
Hydrated silicic acid was obtained in the same manner except that the remaining amount of sulfuric acid added was 1.27 and the reaction temperature was changed. Table 1 shows the silica concentration (C), acid addition ratio (A), reaction temperature (T) and (X) values. Table 1 shows the results of the same measurements and tests as in Example 1. Comparative Example 7 In Comparative Example 6, the amount of sulfuric acid added in the first stage was
Hydrated silicic acid was obtained in the same manner as in Example 1.16, except that the remaining amount of sulfuric acid added was changed to 1.70, and the reaction temperature was changed. Table 1 shows the silica concentration (C), acid addition ratio (A), reaction temperature (T) and (X) values. Further, the results of measurements and tests similar to those in Example 1 are shown in Table 1.

【table】

【table】 [Brief explanation of the drawing]

FIGS. 1, 2, and 3 each show a schematic diagram showing a method for measuring oil absorption rate. Further, 1 indicates a container, 2 indicates a sample, 3 indicates a weight, 4 indicates a watch glass, and 5 indicates boiling oil.

Claims (1)

[Claims] 1. When producing hydrated silicic acid by adding a mineral acid to an aqueous alkali silicate solution in multiple stages, the ratio of acid addition in the first stage (A) to the total acid addition amount is 20 to 50%; The silica concentration (C) in the solution when adding the second stage of acid is 2 to 6.
g/100c.c., and the reaction temperature (T) is within the range of 70 to 100°C, and the formula X = {1/T-65+(A/10)}
The reaction is carried out under conditions where the value of
Method for producing cc/g hydrated silicic acid.